Process for the oxychlorination of an alkane using a solid solution catalyst containing iron cations

ABSTRACT

An alkane is reacted with oxygen and available chlorine in the presence of a solid solution catalyst containing iron cations to yield unsaturated hydrocarbons and chlorinated saturated and unsaturated hydrocarbons. In a preferred embodiment of the process, ethane is reacted with oxygen and available chlorine in the presence of a solid solution catalyst containing iron cations to yield vinyl chloride, ethylene, and other valuable by-products. The conversion of ethane to products approaches 100 percent, vinyl chloride is prepared in up to 40 mole percent yield, and the combined yield of vinyl chloride, ethylene dichloride, ethyl chloride, and ethylene is up to 90 mole percent.

CROSS REFERENCE TO RELATED APPLICATION

This is a division of application Ser. No. 950,119, filed Oct. 10, 1978,now U.S. Pat. No. 4,375,569; which is a division of application Ser. No.741,910 filed on Nov. 15, 1976 and now U.S. Pat. No. 4,119,570; which inturn is a continuation-in-part of Ser. No. 564,794 filed on Apr. 3, 1975and now abandoned.

BACKGROUND OF THE INVENTION

The reaction of an alkane in the presence of a catalyst to formunsaturated hydrocarbons is well known. If a chlorine source is present,chlorinated saturated and unsaturated hydrocarbons are also produced.Perhaps the most familiar of such processes is the preparation of vinylchloride.

Vinyl chloride (CH₂ ═CHCl) itself can be prepared using a number ofdifferent processes. Two familiar processes are (1) thehydrochlorination of acetylene and (2) the oxychlorination of ethyleneto form dichloroethane which in turn is dehydrohalogenated to form vinylchloride (see C. A. Schildknecht, Vinyl and Related Polymers, John Wileyand Sons, Inc., N.Y., N.Y. (1952), pages 388-390, and U.S. Pat. No.2,847,483). As acetylene is more expensive than ethylene, the latterprocess is economically favored, and much activity is noted in this artarea (see U.S. Pat. Nos. 3,634,330; 3,454,663; 3,448,057; and3,624,170). Ethylene, in turn, can be prepared by the oxydehydrogenationof ethane (see U.S. Pat. No. 3,769,362). The processes have beencombined so that vinyl chloride can be directly produced using ethane asa feed stock (see U.S. Pat. Nos. 2,838,577; 3,658,933; 3,658,934, and3,551,506). It is the nature of the processes which use ethane as a feedstock to produce vinyl chloride and ethylene, along with other valuableproducts such as ethylene dichloride and ethyl chloride. As ethylene,ethylene dichloride, and ethyl chloride can be readily reacted to formmore vinyl chloride, the processes are often rated and compared on theirability to yield all four products. However, high conversion of ethaneto products and high yield of vinyl chloride is particularly desired.

The present invention is directed to an improved process for theoxychlorination of an alkane and particularly for the preparation ofethylene and vinyl chloride from ethane which process employs specificsolid solution catalysts containing iron. The catalysts of the inventionexhibit improved activity and longer lifetimes compared to conventionaliron containing catalysts. Catalysts containing iron are known to theart; see U.S. Pat. Nos. 3,849,339; 3,769,362; 3,723,351; 3,703,593;3,658,934; 3,658,933; 3,207,809; 2,847,483; and 2,674,633, U.S.Publication No. B 380,979, and British Pat. No. 1,039,369. An article inthe Journal of The American Ceramic Society, Vol. 43, No. 7 (1960), page367, discloses compounds of lanthanum and iron and recently issued U.S.Pat. No. 3,904,553 discloses certain solid solutions as having activityas catalysts.

SUMMARY OF THE INVENTION

The invention comprises an improved catalyst and process for theoxychlorination of an alkane and particularly for the preparation ofethylene and vinyl chloride from ethane. The catalyst is a solidsolution catalyst containing iron cations substituted for cations of ahost lattice selected from the group consisting of a α-Al₂ O₃, β-Al₂ O₃,Ba Al₁₂ O₁₉, Ba₀.50 Ce₀.17 Ag₀.33 Al₁₂ O₁₉, and α-Cr₂ O₃. Use of thenovel catalysts in the process of the invention produces yields of up to40 mole percent of vinyl chloride and up to 90 combined mole percent ofvinyl chloride, ethylene, ethyl chloride, and ethylene dichloride. Thecatalysts can remain active for up to 100 hours without substantial lossor iron, and can then be readily reactivated by heating the catalyst toabove about 1200° C.

DETAILED DESCRIPTION OF THE INVENTION

An alkane, such as ethane, is combined with oxygen and a chlorine sourcesuch as hydrogen chloride and is oxychlorinated in the presence of asolid solution catalyst of the invention to prepare unsaturatedhydrocarbons, saturated chlorinated hydrocarbons, and unsaturatedchlorinated hydrocarbons such as ethylene, ethyl dichloride, and vinylchloride and other valuable by-products. Depending upon feed and reactorconditions, about 5 to 40 mole percent yield of unsaturated chlorinatedhydrocarbon such as vinyl chloride and up to a 90 mole percent totalyield of products such as vinyl chloride, ethylene dichloride, ethylchloride, and ethylene can be obtained. Conversion of alkane to productscan approach 100 mole percent.

The alkane that can be employed in the process of the invention can have1 to about 12 or more carbon atoms. Examples of such alkanes aremethane, ethane, propane, n-butane, t-butane, n-hexane, n-octane,isooctane, n-decane, and the like. More preferably, the alkane employedhas 2 to about 6 carbon atoms, exemplified by ethane, propane, n-butane,and n-hexane, Most preferably, the alkane used in the process of theinvention is ethane. Hereinafter, reference will be made to the use ofethane in the process, although it is understood that other alkanes canbe likewise employed.

In the process, ethane, oxygen, and a chlorine source are placed into areactor vessel containing the solid solution catalyst containing ironcations. The process contemplates the use of any standard technique foroxychlorination concerning the type of operation, reactor size anddesign, and the like. The process can be operated as a bath process, butis preferably conducted as a continuous process wherein reactants andproducts are continuously added and withdrawn. The solid solutioncatalyst can be supported or unsupported, and can be fixed as in a bedor present as particles that can readily fluidize during operation. Apreferred process is to employ the solid solution catalyst inparticulate form that will fluidize during operation of the processthereby establishing maximum contact with the reactants. Such processesare known as fluid bed processes, and the reactors designed for such areknown as fluid bed reactors. A typical reactor is designed such that oneor more gaseous reactants is introduced in the reactor at a point belowthe catalyst bed, and the gas pressurized through the bed, lifting andsuspending the catalyst in the reactor volume. Other reactants can beadded at appropriate levels above, below, or any point in the fluidcatalyst bed. Normally, products are withdrawn from the top portion ofthe reactor above the fluid bed and collected or further treated asdesired.

Although the process contemplates the use of known operating techniquesand reaction conditions, certain conditions are herein stated as usefuland practical. The reactants comprise ethane, oxygen (usually used inthe form of air), and a chlorine source. The chlorine can be supplied asanhydrous hydrogen chloride or as a mixture of anhydrous chlorine andhydrogen chloride. Using one mole of ethane as a basis, the hydrogenchloride is used at from about 0.1 mole to about 10 moles or more. Morepreferably, the hydrogen chloride is used at a level of from about 0.5mole to 5 moles per mole of ethane. In general, the use of a higherratio of hydrogen chloride to ethane increases the yield of vinylchloride and other chlorinated products and decreases the yield ofethylene. However, high levels of hydrogen chloride (above 5 moles)increase the amount of hydrogen chloride to recycle. Excellent yields ofvinyl chloride have been obtained using about 2 to 4 moles of hydrogenchloride per mole of ethane.

Oxygen, preferably in the form of dry air, is used at from about 0.1mole to about 1.5 moles of oxygen to one mole of ethane. A morepreferred level is from about 0.5 mole to about 1 mole. The use oflevels of oxygen of over about 1 mole results in increased production ofpolychlorinated products, but also increases production of carbonoxides. Excellent yields of vinyl chloride have been obtained using alevel of oxygen of from about 0.7 mole to 1.0 mole per mole of ethane.

Ethane, oxygen, and hydrogen chloride are put into the reactor asreactants. Temperature of reaction range from about 400° C. to about650° C., and more preferably from about 475° C. to about 600° C.Materials withdrawn from the reactor in the product stream comprisevinyl chloride, ethylene, chlorinated products such as ethylenedichloride and ethyl chloride, carbon oxides (CO and CO₂), water andunreacted ethane and hydrogen chloride. Another product found in theexit stream is iron, presumedly in the form of iron chlorides such asferric chloride. The iron present in the product stream includes ironlost from the catalyst.

The improved feature of the oxychlorination process is the use ofspecific solid solution catalysts containing iron cations as theoxychlorination catalysts. The catalyst itself is a solid solution ofiron cations in specific host lattice selected from the group consistingof α-Al₂ O₃, β-Al₂ O₃, BaAl₁₂ O₁₉, Ba₀.50 Ce₀.17 Ag₀.33 Al₁₂ O₁₉ andα-Cr₂ O₃. This is in contrast to most standard catalysts wherein anactive ingredient such as cupric chloride or iron oxide is merelyabsorbed onto the surface of a support structure or material. Thedifference between the catalysts of the invention and other knowncatalysts can be distinguished in the physical state of the catalyst andin the activity of the catalyst.

A solid solution catalyst is a true solution wherein cations aresubstituted for host lattice ions in the catalyst structure. An X-raydiffraction pattern of a solid solution catalyst is characteristic ofthe diffraction pattern of the host lattice. For example, a solidsolution catalyst of iron cations in α-Al₂ O₃ will exhibit an X-raydiffraction pattern characteristic of α-Al₂ O₃. In contrast, if iron inthe form of Fe₂ O₃ is merely absorbed onto α-Al₂ O₃, the X-raydiffraction pattern will show the presence of both Fe₂ O₃ and α-Al₂ O₃.

A distinguishing feature of the solid solution catalysts, compared toimpregnated catalysts, is in the increased retention of iron upon use.For example, a solid solution catalyst containing iron cations in anα-Al₂ O₃ host lattice used at a given set of reaction conditions lostabout 15% by weight of its original iron content after about 100 hoursof use. In contrast, a catalyst comprised of ferric oxide merelyabsorbed onto α-Al₂ O₃, operating under the same set of conditions, lostover 80% by weight of its original iron content after about 100 hours ofuse.

Another distinguishing feature of the solid solution catalysts of theinvention is that the catalysts can be regenerated. This is accomplishedby heat treating the solid solution catalyst by firing the catalyst atabout 1200° C. or above to redistribute the iron cations to replacethose lost from the active sites. The reactivation of the solid solutioncatalyst is not merely a reoxidation of a reduced catalyst for heatingin pure oxygen at 550° C. for two hours does not restore activity.

Solid solution catalysts containing iron cations can be of differenttypes. The iron exits as ferric (Fe⁺³) and/or ferrous (Fe⁺²) ions. Theferric ion is the active ion in the catalyst. However, as the ferrousion can oxidize to a ferric ion in the process, the use of solidsolution catalysts containing ferrous ions are within the scope of theinvention.

One type of solid solution consists of iron ions substituted for hostlattice ions wherein the iron ion(s) has a different oxidation statethan that of the host lattice ion. An example of such a solid solutionis Zn(Ti_(x) ⁺⁴ Fe_(2-2x) Fe_(x) ⁺²)O₄ wherein x is from 0 to 1. Theiron, zinc, and titanium ions exist in an orderly arrangement, and thecatalyst exhibits a single phase X-ray diffraction pattern. Another suchsolid solution catalyst is (Al_(2-2x) ⁺³ Fe_(x) ⁺² Ti_(x) ⁺ 4)O₃ whereinx is greater than 0 and up to 1. The iron, titanium and aluminum ionsexist in an orderly arrangement, and the catalyst exhibits a singlephase X-ray diffraction pattern. Other solid solution catalysts wherethe substituting iron ion(s) has an oxidation state different from thatof the host lattice ion(s) exist.

A second type of solid solution containing iron cations is that whereinthere is direct substitution of iron ions for host lattice ions whereinboth ions have common oxidation states. An example of this type ofcatalyst is (Fe_(x) ⁺³ M_(2-x) ⁺³)O₃ wherein x is greater than 0 andless than 2, and M is a metal such as Al or Cr. As the ferric +3 ion isgreater in size than an aluminum +3 ion, the solubility of the ferricion in aluminum oxide is somewhat limited. Hence, the solid solutioncatalysts wherein M is aluminum encompass materials of the formulawherein x has a practical upper limit of about 0.15.

The solid solution catalysts of the invention are the type containingiron cations wherein there is direct substitution of iron ions for hostlattice ions wherein both ions have the same or common oxidation state.Examples of these catalysts are a solid solution catalyst of ferric ionin alpha-aluminum oxide (α-Al₂ O₃) or in alpha-chromium oxide (α-Cr₂O₃). The basic solid solution catalyst of iron cations in α-Al₂ O₃ orα-Cr₂ O₃ can contain other metal ions such as potassium (as the oxide),barium (as the oxide), Ce, and Ag (all as the oxides). Hence, otherexamples of solid solution catalysts of the invention which wereprepared are iron in K₂ O.11Al₂ O₃ (or the iron in β-Al₂ O₃ solidsolution), iron in BaO.6Al₂ O₃ (or the iron in BaAl₁₂ O₁₉ solidsolution), and iron in Ba₀.50 Ce₀.17 Ag₀.33 Al₁₂ O₁₉ (wherein Ce and Agare in partial replacement of Ba).

Solid Solution Catalyst Identification and Characterization

The solid solution catalysts of the invention contain iron cations inspecific host lattices and have X-ray diffraction patternscharacteristic of the host lattice material. Solid solutions are knownto exist (see C. S. Barrett, Structure of Metals, CrystallographicMethods, Principles, and Data, 2nd Ed., McGraw-Hill Book Co., Inc. N.Y.,N.Y. (1952), at pages 220 et seq.); V. L. Moruzzi et al, PhaseEquilibria in the System La₂ O₃ -Iron Oxide in Air, J. Amer. Chem. Soc.,Vol. 43, No. 7 (1960), pages 367-372; and Carmen et al, Electron SpinResonance of α-Chromia-Alumina Solid Solutions, J. Physical Chem., Vol.72 (1968), pages 2562-2566).

The catalyst is first identified and characterized by analyzing it todetermine what elements it contains. This can be done using well knowntechniques such as chemical analysis, atomic absorption spectroscopy,X-ray fluorescence spectroscopy, and optical microscopy. For example,the solid solution catalyst of iron in alpha-aluminum oxide would showiron, aluminum, and oxygen to be present in the catalyst. The presenceand quantity of iron in the catalyst can be readily determined using astandard method of chemical analysis such as the dichromate method forthe determination of iron. The amount of iron in the solid solutioncatalysts is limited by the solubility of the ions in the host lattice.The solid solution catalysts can contain from about 0.5 percent to 70percent by weight and more preferably from about 1 percent to about 15percent by weight of iron in the catalyst, the iron expressed as ironoxide.

The second step of identification and characterization involves runningan X-ray diffraction scan on the catalyst. The X-ray diffraction scanwill show a pattern of peaks, which peaks have positions and intensitiesdistinctive of the crystalline phases which are present. The X-raydiffraction peak positions and intensities of the catalyst can becompared to peak positions and intensities of known crystalline phasesthat are published (in the ASTM Powder Diffraction File, for example),or that are experimentally obtained. For example, a catalyst comprisedof iron oxide merely impregnated on or absorbed on aluminum oxide willhave an X-ray diffraction pattern of peak positions showing the distinctpeak positions and intensities of iron oxide and aluminum oxidecrystalline phases.

In contrast, the X-ray diffraction pattern of a solid solution catalystcontaining iron shows the positions of the X-ray diffraction peaks inthe solid solution catalyst to be shifted from the peak positions in theX-ray diffraction pattern of the host lattice. The shift in peakpositions may be accompanied by changes in the relative intensities ofthe peaks, but the intensity changes are generally small.

The shift in X-ray diffraction peak positions when solid solutions areformed results from the expansion (or contraction) of the dimensions ofthe unit cell of the crystalline phase of the host lattice. Thedimensions of the unit cell of the host lattice are changed due to thesubstitution of iron cations for cations of the host lattice. If thecation is larger than the cation it displaces, the unit cell dimensionswill increase in size to accommodate the larger cation. The amount ofexpansion (or contraction if the iron cation is smaller than the hostlattice cation it displaces) of the unit cell dimensions can bedetermined by calculating the lattice parameters of the unit cell of thesolid solution phase and comparing these lattice parameters to thelattice parameters of the unit cell of the host. A change in latticeparameters due to iron substitution in a crystalline host lattice isfrequently in accordance with Vegard's law (see page 221 of theabove-cited reference). Since a change in the lattice parameters causesa change in the X-ray diffraction peak positions, a comparison of theX-ray diffraction pattern of the catalyst and the pattern of the hostlattice will show whether a solid solution catalyst has been prepared.

Alternately, a more accurate method of confirming the preparation of asolid solution catalyst is to experimentally run X-ray diffraction scansof the prepared catalyst and of the host lattice and then calculate thelattice parameters of each. If the values obtained for the latticeparameters of the catalyst and host lattice are different, a solidsolution catalyst has been prepared. If the geometry and dimensions(lattice parameters) of the unit cell of the host lattice is not known,it can be determined using established methods for indexing andinterpreting X-ray diffraction patterns (see L. V. Azaroff and M. J.Buerger, The Powder Method In X-Ray Crstallography, McGraw-Hill BookCo., Inc., N.Y., N.Y. (1958), chapters 6 to 13). The high 2θ values(where θ is the Bragg angle) are normally used to calculate the latticeparameters.

In summary, the solid solution catalysts of the invention can beidentified and characterized by (1) the presence of iron in thecatalyst, and (2) the X-ray diffraction pattern of the catalyst. Theiron is present as cations substituted in the host lattice for cationsof the host lattice. The iron content can be measured using standardanalysis techniques. The X-ray diffraction pattern of the solid solutioncatalyst will exhibit peak positions characteristic of the host latticebut shifted due to the presence of the iron cations in the host lattice.Lattice parameters calculated for the host lattice and the solidsolution catalyst will differ. The X-ray diffraction pattern of thesolid solution catalysts of the invention can exhibit extraneous peaksin the pattern due to formation of crystalline compounds other than thesolid solution catalyst itself. For example, in preparing the iron inbeta-alumina solid solution catalyst, the host lattice containspotassium, and K₂ O is formed and peaks due to the presence of K₂ O areseen in the X-ray diffraction pattern.

Preparation of Solid Solution Catalysts

The solid solution catalysts used in the Examples were prepared by firstimpregnating a host lattice precursor with an iron salt that yields theoxide upon heating, then heating the impregnated host lattice precursorto about 550° C. followed by heating to 1200° C. or more.

The first heating converts the salts to oxides, and initiates conversionof the host lattice precursor to the host lattice. The second heatingcompletes the formation of the host lattice and produces a rearrangementof the metal atoms between the metal ions in the host lattice and theiron ions. The catalyst prepared is a solid solution catalyst containingiron and having a distinctive X-ray diffraction pattern.

The solid solution catalyst can be prepared in other different ways.Another method is to physically admix iron oxide and the host latticematerial and heat the mix to above about 1100° C. to allow dissolutionand substitution of the iron ions for those of the host lattice, andformation of the stabilized catalyst. Heating conditions can vary forthe nature of the host lattice employed, but are above about 1100° C.

A third method of preparation is to use the so-called sol-gel processwherein an iron salt and a salt precursor of the host lattice are mixedtogether as solutions and a base is added to coprecipitate out a mixtureof the corresponding hydrated oxides. For example, ferric nitrate andaluminum nitrate can be dissolved in water and ammonium hydroxide addedto the solution to coprecipitate a mixture of hydrated iron and aluminumoxides. The mix is then heated to above about 1100° C. to perfectdissolution and substitution of the iron ions for aluminum ions.

A fourth method is to dissolve an iron salt in a solvent such as wateror ethanol and use the solution to impregnate the host lattice, then dryand heat the mix to above about 1100° C. to cause the metal salt todecompose upon heating to yield the oxide and to substitute the ironions for those of the host lattice.

In all of these methods a metal oxide precursor can be used in place ofthe metal oxide per se. The precursor, which is typically a salt of themetal, decomposes on heating to yield the oxide form of the metal.Examples of iron oxide precursors are iron chloride, iron sulfate, ironformate, iron oxalate, iron citrate, iron nitrate, and the like.

The exact preparation of an iron in α-Al₂ O₃ solid solution catalyst isshown in the following example. Alumina trihydrate is used as the hostlattice precursor, and an alcohol solution of ferric nitrate is used asthe impregnating solution. 551 grams of alumina trihydrate (Al₂ O₃.3H₂O), sold commercially as Alcoa C-31, was placed into a porcelain dish. Asolution of 76 grams of ferric nitrate, Fe(NO₃)₃.9H₂ O, dissolved in 250milliliters of absolute ethanol was added to the alumina trihydrate inthe dish and the mix stirred as it was heated to evaporate the ethanol.The impregnated material was then heated in air for 16 hours at 550° C.to dehydrate the alumina trihydrate to aluminum oxide and to decomposethe ferric nitrate to ferric oxide. The impregnated aluminum oxide waspassed through an 80 mesh screen and then placed into a platinum/rhodiumcrucible and heated in the air for 16 hours at 1200° C. The catalystobtained was sieved through screens and the portion passing through 80mesh and held on 200 mesh was used for oxychlorination experiments.

The prepared catalyst was a solid solution catalyst of about 4% byweight of iron, expressed as the ferric oxide, in α-aluminum oxide (ironin α-Al₂ O₃). The X-ray diffraction pattern of the solid solutioncatalyst exhibited a 0210 peak at 88.929° 2θ and a 134 peak at 91.079°2θ. The α-Al₂ O₃ host lattice exhibited its 0210 peak at 89.031° 2θ andits 134 peak at 91.211° 2θ. Hence, the peak positions of the catalysthad shifted due to the presence of the iron cations in the aluminumoxide host lattice. The interplanar spacing between the planes in thecrystalline lattice represented by the 0210 and 134 peak positionsincreased, going from a "d" value of 1.0986 Å for α-Al₂ O₃ to 1.0996 Åfor the catalyst for the 0210 peak, and from 1.0780 Å to 1.0792 Å forthe 134 peak. The lattice parameters calculated for the α-Al₂ O₃ were:"a" value=4.758 Å and "c" value=12.986 Å, while the lattice parametersfor the solid solution catalyst were: "a" value=4.763 Å and "c"value=12.997 Å. The lattice parameters of this solid solution catalystare larger than those of the α-Al₂ O₃ host lattice due to thesubstitution of the larger iron cations for aluminum cations in the hostlattice.

Solid solution catalysts of iron cations in α-Al₂ O₃ were also preparedusing a larger amount of ferric nitrate in solution to yield a solidsolution catalyst having about 11% by weight of iron, expressed as Fe₂O₃, in the α-Al₂ O₃ host lattice. Likewise, other metal compounds whichyield iron oxide on heating can be used in solution with other hostlattices such as K₂ O.11 Al₂ O₃ (β-Al₂ O₃) and BaO.6 Al₂ O₃ (BaAl₁₂O₁₉).

The solid solution catalysts of the invention can be used in the processin the form of a fixed bed, a fluidized bed, on a fixed support, on afluidized support, or in a number of ways well known to the art.Although in the examples the process used is a fluidized bed process, itis understood that other well known techniques can be employed. Thefollowing Examples are given to further illustrate the invention.

EXAMPLES Oxychlorination Process

Solid solution catalysts of the invention were used in anoxychlorination process to react ethane to vinyl chloride. The reactionswere conducted in a fluid bed reactor wherein the ethane, oxygen used inthe form of air, and anhydrous HCl were premixed at a set molar ratio ofreactants and the mixture fed into a heated reactor near the bottom. Thecatalyst was of a particle size (particles passing between 80 mesh and200 mesh screens) and the feed rate selected to suspend the catalystparticles in the gas stream during the reaction. Contact times were fromabout 5 seconds to about 10 seconds. Products were withdrawn from thetop of the reactor as gases, scrubbed with water and analyzed using agas chromatograph. The process was run as a continuous process for timesof 1 hour up to 140 hours per run.

The following examples detail experiments conducted using various moleratios of reactants, various temperatures and times of reaction, anddifferent solid solution catalysts.

EXAMPLE I

Experiments were conducted to compare ethane conversion, yield of vinylchloride, and iron loss between a solid solution catalyst of thisinvention and a catalyst prepared by a standard method. The solidsolution catalyst used was the iron in α-Al₂ O₃ solid solution catalystprepared in the detailed procedure given above, and consisted of a solidsolution of 4% by weight of iron, expressed as Fe₂ O₃, in α-Al₂ O₃. Theother standard catalyst employed in the comparison was prepared byimpregnating α-aluminum oxide with a solution of ferric nitrate, dryingthe mix, and then heating the mix for 16 hours at 550° C. to dehydratethe aluminatrihydrate and to decompose the ferric nitrate to ferricoxide. The preparation is the same as disclosed in the preparation ofthe solid solution catalyst except that no heating to 1200° C. was done.

The reactants were fed into the reactor at a mix of 1 mole ethane/1 moleof oxygen (as air)/4 moles of anhydrous hydrogen chloride. Contact timethroughout the runs ranged from 5.7 to 7.8 seconds. Temperature ofreaction was 550° C. Results are given in the following tables.

    ______________________________________                                        Time       Mole % Conversion                                                                           % Yield of                                           (Hrs.)     of Ethane     Vinyl Chloride                                       ______________________________________                                                 Iron in α-Al.sub.2 O.sub.3                                              Solid Solution Catalyst                                              2          97.8          32.1                                                 5          98.2          33.4                                                 26         97.8          34.1                                                 48         98.2          33.6                                                 84         97.9          34.5                                                 102        91.8          24.2                                                 107        93.6          23.1                                                          Comparative Catalyst                                                 1          99.0          23.8                                                 5          98.2          26.8                                                 31         99.2          26.9                                                 55         99.2          28.6                                                 62         98.4          31.0                                                 99         97.4          29.6                                                 109        99.0          27.7                                                 119        98.8          24.2                                                 141        97.6          17.5                                                 ______________________________________                                    

The data show that the solid solution catalyst of the invention and thecomparative catalyst are somewhat comparable in mole % conversion ofethane. However, the greater activity of the solid solution catalyst isdemonstrated by the higher yields of vinyl chloride.

Another major difference between the two catalysts appears in the ironloss sustained by each catalyst. Results are reported in the followingtable. Iron content was determined using the dischromate process for thedetermination of iron.

    ______________________________________                                        Time        Percent Iron Retained                                             (Hrs.)      Solid Solution                                                                            Comparative                                           ______________________________________                                        0           100         100                                                   26          97.1        --                                                    28          --          67.1                                                  48          94.9        --                                                    51          --          43.6                                                  83          86.9        --                                                    101         --          15.0                                                  107         85.4        --                                                    ______________________________________                                    

The data show that after about 100 hours of reaction time, the solidsolution catalyst lost only about 15% by weight of its initial ironcontent, while the other standard catalyst lost about 85% by weight ofits iron.

The solid solution catalysts of the invention can be regenerated whenthey show a loss in activity to give conversions and yields comparableto original values. The comparative catalyst, having lost more of itsiron when its activity decreased, could not be regenerated. Theconversion and yield data in the preceding tables show that at about 15%loss of iron in the solid solution catalyst (at about 100 hours), theactivity of the catalyst decreased. The following experiment shows theregeneration of the solid solution catalyst. The solid solution catalystof 4% by weight of iron, expressed as Fe₂ O₃, in α-Al₂ O₃ was firstheated to 550° C. for two hours in pure oxygen and then evaluated forits activity. No increase in activity was observed. This demonstratesthat the regeneration is not simply a reoxidation process. The solidsolution catalyst was then heated to 1300° C. for 20 hours and againevaluated for its activity. The catalyst activity was excellent andcomparable to its original activity. Data are given in the followingtable.

    ______________________________________                                                    Solid Solution Catalyst                                                       Mole % Conver-                                                                            % Yield of                                                        sion of Ethane                                                                            Vinyl Chloride                                        ______________________________________                                        Original Catalyst                                                             at 2 hours    97.8          32.1                                              at 5 hours    98.2          33.4                                              at 107 hours  93.6          23.1                                              Oxidation Treated                                                                           90.9          21.9                                              at 1.25 hours                                                                 Heat Treated (1300° C.)                                                              98.4          34.0                                              at 5 hours                                                                    ______________________________________                                    

EXAMPLE II

A solid solution catalyst of 4 % by weight of iron, expressed as Fe₂ O₃,in α-Al₂ O₃ (the same as that employed in Example I) was used in theoxychlorination of ethane. The process herein is similar to that ofExample I but for the mole ratio of reactants. The feed stream comprised1 mole of ethane/1 mole of oxygen (as air)/2 moles of anhydrous hydrogenchloride rather than 4 moles of HCl as in the previous example. Contacttime was 6.5 to 7.1 seconds. The use of a lower ratio and amount of HClin the process results in slightly lower conversions of ethane, loweryields of vinyl chloride, higher yields of ethylene, and less iron lossfrom the catalyst (about one-half the iron loss shown in the previousexample). The following table shows the data obtained.

    ______________________________________                                                             % Yield of                                               Time   Weight %  Mole % Conversion                                                                           Vinyl                                          (Hours)                                                                              Iron Loss of Ethane     Chloride                                                                             Ethylene                                ______________________________________                                        17     --        94.9          21.6   50.2                                    20     --        94.8          21.9   49.4                                    41     --        94.8          21.0   51.1                                    47     3.0       --            --     --                                      67     --        94.4          22.1   47.1                                    94     --        94.2          21.9   46.5                                    107    8.7       94.7          20.9   52.5                                    115    --        94.4          20.6   51.3                                    139    --        91.8          18.1   51.0                                    ______________________________________                                    

EXAMPLE III

A solid solution catalyst of 11% by weight of iron, expressed as Fe₂ O₃,in α-Al₂ O₃ prepared as above was evaluated in an oxychlorinationprocess similar to that in Example II (i.e., a 1/1/2 mole ratio ofethane/oxygen/HCl and a contact time of 6.7 to 7.1 seconds). The higherlevel of iron in the catalyst resulted in somewhat higher conversionsand yields. After 140 hours of reaction time, the solid solutioncatalyst was regenerated and reactivated by heat treating it at 1300° C.

    ______________________________________                                                          % Yield of                                                  Time    Mole % Conver-  Vinyl                                                 (Hrs.)  sion of Ethane  Chloride Ethylene                                     ______________________________________                                         1      93.4            26.6     48.9                                         20      94.5            26.1     48.4                                         46      95.9            26.6     50.6                                         69      95.6            26.7     50.2                                         89      95.4            25.6     50.8                                         100     97.9            22.4     61.1                                         116     97.8            19.4     60.7                                         140     98.4            19.0     59.1                                         .sup. 2.sup.a                                                                         99.0            24.7     55.6                                         ______________________________________                                         .sup.a Catalyst heat treated at 1300° C. to regenerate it         

EXAMPLE IV

A solid solution catalyst of Fe³⁺ ions substituted for Al³⁺ ions in aβ-Al₂ O₃ host lattice was prepared. A mixture of aluminum trihydrate andpotassium carbonate was impregnated with an ethanol solution of ferricnitrate. The mix was dried, ground, and heated at 560° C. for 16 hoursto dehydrate the aluminum trihydrate, and decompose the ferric nitrateto ferric oxide. The material was then heated at 1200° C. for 16 hoursto decompose the potassium carbonate to potassium oxide and to yield theiron in β-Al₂ O₃ solid solution catalyst which can be expressed as (K₂O.11 Fe₂ O₃ in K₂ O.11 Al₂ O₃). The final catalyst composition had aconcentration of iron, expressed as the oxide, of about 4% by weight.

The iron in β-Al₂ O₃ solid solution catalyst was evaluated in anoxychlorination process using ethane. The data given in the followingtable was generated in a continuous, fluid bed reactor process whereinthe ethane/oxygen (as air)/HCl mole ratio was 1/1/4, temperature ofreaction was 500° C., and contact time was about 7 seconds.

    ______________________________________                                        β-Al.sub.2 O.sub.3 Solid Solution Catalyst                               Time    Mole % Conver-                                                                              % Yield of                                              (Hrs.)  sion of Ethane                                                                              Vinyl Chloride                                                                             Ethylene                                   ______________________________________                                         6      96.4          38.5         26.3                                       24      97.6          41.4         25.3                                       32      96.6          41.2         23.8                                       69      96.2          38.4         27.7                                       74      92.8          33.7         23.4                                       88      94.5          31.4         28.8                                       100     91.3          25.3         26.1                                       ______________________________________                                    

The data show that good mole percent conversions of ethane and highyields of vinyl chloride and ethylene are obtained using the β-Al₂ O₃solid solution catalyst containing iron cations. The yields of vinylchloride are higher and yields of ethylene are lower than those obtainedusing the iron in α-Al₂ O₃ solid solution catalyst (see Examples I andII).

EXAMPLE V

Using the β-Al₂ O₃ solid solution catalyst prepared in Example IV, aseries of oxychlorination experiments were run varying temperature ofreaction and mole ratios of oxygen and HCl in the feed mixture. Contacttimes varied from about 6 to about 10 seconds. The data listed belowwere obtained from a continuous, fluid bed reactor process whereintemperature or molar feed ratio was varied and the process allowed toreach a steady-state before measuring conversion and yields.

    __________________________________________________________________________                                                  Total                           Reaction Ethane/O.sub.2 /                                                                     Mole %                        Combined                        Tempera- HCl Mole                                                                             Conversion                                                                          % Yield of   Ethylene                                                                            Ethyl                                                                              Yield,                          Sample                                                                            ture (°C.)                                                                  Ratio  of Ethane                                                                           Vinyl Chloride                                                                        Ethylene                                                                           Dichloride                                                                          Chloride                                                                           Percent                         __________________________________________________________________________    1   425  1/1/4  66.1  12.0     9.3 6.6   47.2 75.1                            2   450  1/1/4  81.3  19.9    13.5 6.4   34.1 73.9                            3   475  1/1/4  94.8  35.2    23.6 2.3   15.1 76.2                            4   500  1/1/4  96.4  38.5    26.3 5.4    9.9 80.1                            5   550  1/1/4  98.6  38.0    34.1 3.5    3.4 79.0                            6   500  1/1/4  97.6  41.4    25.3 4.1    7.9 78.7                            7   500  1/1/3  96.5  37.6    20.1 3.1   10.4 71.1                            8   500  1/1/2  92.7  26.0    25.0 4.5   19.8 75.3                            9   500  1/0.8/4                                                                              93.6  36.4    29.8 4.5   15.5 86.2                            10  500  1/0.8/3                                                                              91.1  30.5    32.5 4.6   20.9 88.5                            11  500  1/0.8/2                                                                              89.5  27.8    29.9 5.0   23.7 86.4                            12  500  1/0.7/4                                                                              98.1  31.3    31.3 5.2   21.7 89.5                            13  500  1/0.7/3                                                                              88.7  31.1    33.6 3.9   19.2 87.8                            14  500  1/0.7/2                                                                              80.1  23.3    34.2 2.8   26.2 86.5                            __________________________________________________________________________

The data show that increasing temperature increases mole percentconversion and yields of vinyl chloride and ethylene. A minimumtemperature of about 400° C. is necessary to produce minimal yields ofvinyl chloride. A decreasing molar HCl ratio resulted in a decreasedmole percent conversion of ethane, decreased vinyl chloride yield, andan increased ethyl chloride yield, while ethylene dichloride andethylene yield were relatively unaffected. A decreasing molar oxygenratio decreases mole percent conversion of ethane and decreases vinylchloride yield, while ethylene and ethyl chloride yields increase. Totalcombined yield is relatively unaffected by the process changes, exceptfor a noted increase in combined yield as the oxygen ratio decreased.

EXAMPLE VI

A solid solution catalyst was prepared wherein Fe³⁺ ions are substitutedfor Al³⁺ ions in a host lattice of barium aluminate (BaAl₁₂ O₁₉). Thecatalyst was prepared by impregnating alumina trihydrate with a watersolution of ferric nitrate and barium nitrate, drying the mix, andheating at 660° C. for 16 hours to dehydrate the alumina trihydrate anddecompose the nitrates into oxides. The material was then heated at1350° C. for 16 hours to produce a solid solution catalyst which can beformulated as a solid solution of BaFe₁₂ O₁₉ in BaAl₁₂ O₁₉. Twocatalysts containing 3.83% by weight and 7.66% by weight BaFe₁₂ O₁₉ inBaAl₁₂ O₁₉ were prepared.

The barium aluminate solid solution catalysts were evaluated asoxychlorination catalysts following the procedures previously given.Mole ratio of reactants was 1 ethane/1 oxygen/4 HCl, temperature ofreaction was 550° C., and contact time was 6.6 to 7.1 seconds. Incontrast to the use of the iron in α-Al₂ O₃ solid solution catalyst ofExample I, the use of the barium aluminate solid solution catalystsresulted in a higher yield of ethylene and a lower yield of vinylchloride. Mole percent conversion of ethane was comparable using bothcatalysts.

    ______________________________________                                                          % Yield of                                                  Time    Mole % Conver-  Vinyl                                                 (Hrs.)  sion of Ethane  Chloride Ethylene                                     ______________________________________                                        3.83% BaFe.sub.12 O.sub.19 in BaAl.sub.12 O.sub.19                            4       97.1            17.0     59.6                                         21      96.6            17.3     59.8                                         7.66% BaFe.sub.12 O.sub.19 in BaAl.sub.12 O.sub.19                            1       99.2            20.7     59.2                                         29      97.0            19.1     58.9                                         49      94.4            17.6     59.3                                         61      93.5            17.2     59.9                                         88      90.5            15.4     62.1                                         108     88.8            15.5     61.0                                         ______________________________________                                    

EXAMPLE VII

Following the catalyst preparation procedure given in Example VI, asolid solution catalyst was prepared containing aluminum, iron, barium,cesium, and silver ions. Alumina trihydrate was impregnated with a watersolution of ferric nitrate, barium nitrate, cesium nitrate, and silvernitrate. The mix was dried, heated at 660° C. for 16 hours, and thenheated to 1350° C. for 16 hours. The solid solution catalyst preparedcan be formulated as Ba₀.50 Ce₀.17 Ag₀.33 Fe₀.65 Al₁₁.35 O₁₉. Itsstructure is similar to that of the catalyst prepared in Example VI, thedifference being partial replacement of Ba ions by a combination of Ceand Ag ions.

The solid solution catalyst was evaluated as an oxychlorinationcatalyst. Process and reaction conditions employed were the same as inExample VI. The use of the complex barium aluminate solid solutioncatalyst resulted in slightly higher mole percent conversions of ethaneand higher yields of vinyl chloride in comparison with the bariumaluminate solid solution catalyst of Example VI.

    ______________________________________                                                          % Yield Of                                                  Time    Mole % Conver-  Vinyl                                                 (Hrs.)  sion of Ethane  Chloride Ethylene                                     ______________________________________                                         1      98.6            22.9     58.5                                          7      99.3            24.3     56.7                                         31      99.6            22.8     58.3                                         49      99.3            19.3     61.2                                         ______________________________________                                    

We claim:
 1. A process for oxychlorination of ethane comprisingcontacting ethane, oxygen, and hydrogen chloride in the presence of asolid solution catalyst of iron cations in a host lattice of BaAl₁₂ O₁₉at a temperature from about 400° C. to about 650° C. wherein the ethane,oxygen, and hydrogen chloride are employed at a mole ratio of 1 mole ofethane to 0.1 to 10 moles of hydrogen chloride to 0.1 to 1.5 moles ofoxygen, said solid solution catalyst having an iron content of fromabout 0.5 percent to 70 percent by weight, expressed as the oxide, andan X-ray diffraction pattern having peak positions different than thatof its host lattice.